This invention relates to an ink jet type character recording apparatus wherein characters are recorded on a recording paper by charged droplets or minute particles of ink ejected from a nozzle, and more particularly to an ink jet type recording apparatus wherein the control of the fly of the ink jet is effectd by applying a deflecting force thereto in a direction perpendicular to the direction of fly by means of deflection electrode means during recording or nonrecording.
In a prior art ink jet type character recording apparatus, the deflection of the droplets of electrically charged ink is controlled by applying suitable deflection voltages corresponding to the position of a given ink dot of a character to be recorded upon the deflection electrodes of the X and Y axis deflection systems whereby a desired character, pattern or symbol is depicted on the recording paper by a group of dots.
Also other prior art ink jet type character recording apparatus have only an X-axis deflection electrode, and a recording paper only moves to Y-axis direction. Suppose now that a letter is depicted by selecting suitable positions of the dots among a group of 9 .times. 15 dots, that is 9 dots in the direction of the X-axis and 15 dots in the direction of the Y-axis, and that the nozzle for ejecting the ink droplets is positioned on the first line in the X-axis direction. Then, the deflection electrode of the X-axis deflection system is impressed with a deflection voltage which varies as 000050000 with time from dot to dot, whereas on the second line is applied a deflection voltage in the form of 000406000 in accordance with the respective dots. In this manner, by relative movement of the recording paper and nozzle, dots are recorded from line to line to form the letter A, for example, by a group of dots recorded on the recording paper. Considering the deflection voltage utilized to deflect the ejected ink droplets in the X-axis direction, assuming the second line mentioned above, at a point corresponding to the fourth dot, the deflection voltage is increased from zero to a value corresponding to 4, then reduced to zero and again increased to a value corresponding to 6 at a point corresponding to the sixth dot. Thus, the deflection voltage takes the form of a rectangular wave. Where a zero deflection voltage is impressed so that no dot is recorded on the recording paper, the ejected ink droplets are collected by an ink collector disposed on one side of the recording paper. Upon application of the recording voltage, the ejected ink droplets are shifted from the collector to a selected recording position. At this time, it is necessary to quickly vary the deflection voltage from zero to a value corresponding to 4 or 6, thereby requiring a large change in the amplitude of the deflection voltage and causing instability of the operation. Furthermore, due to the switching of the deflection voltage during the fly of the ink droplets or due to the presence of some time constant of the deflection voltage control circuit the ink droplets can not arrive at the desired dot position on the recording paper with the result that the dot is formed on an unwanted position thus making it difficult to depict the correct character. Further, according to the conventional apparatus, each time a character, pattern or symbol on a given line is depicted, the ink ejecting nozzle and the deflection means associated therewith are advanced step by step. According to another arrangement, a plurality of ink ejecting nozzles and deflecting means of number equal to that of the characters of one line are arranged in parallel, and a set of nozzles and deflecting means associated therewith are selected to depict a character. In this manner, all characters on one line are depicted sequentially.
However, when the apparatus is constructed such that characters on one line are depicted with a single nozzle, it is necessary to advance the nozzle one step after one character has been depicted for depicting the next character, thus requiring much time for recording. Where a plurality of nozzles and deflection means are provided for one line, it is necessary to provide a plurality of discrete deflection voltage control circuits for controlling the X and Y axis deflection voltages of respective deflection means for producing character signals, thus complicating the construction of the apparatus.
It is an object of this invention to provide new and improved ink jet type recording apparatus capable of deflecting the stream of ink droplets ejected from a nozzle toward and away from a recording paper so as to describe or not describe characters, patterns or symbols with a deflection voltage whose amplitude is varied in a small width, thereby making it possible to stably record characters, etc. with a minimum time.
Another object of this invention is to provide improved ink jet type character recording apparatus capable of simultaneously recording a plurality of unit characters in one line by means of a plurality of ink dots by providing a plurality of juxtaposed ink nozzles of the same number as that of the unit characters of one line and deflection means for deflecting the stream of ink droplets ejected from the nozzles toward and away from the recording paper.